Manufacturers of hand-held and/or portable electronic devices, such as laptop computers, personal digital assistants (PDA), wireline or wireless telephones, video games and other similar electronic devices, are continually striving to improve customer satisfaction with the usage of input devices, while still fitting the input devices within the form factor of the electronic device. In order to provide common features, such as text messaging, calendar, games, phone book and web access, electronic devices typically include both a display and an input device. The display provides a graphical user interface to the customer to facilitate access to the features. The input device enables selection and implementation of the features (e.g., entering text, controlling cursor position and selecting or “clicking” on features). However, as the size of electronic devices shrinks, the available area on the electronic devices for both a display and an input device becomes limited.
Recently, touch screens have been introduced to the laptop and hand held device industries to reduce the area needed for a display and input device by combining input device functionality with a graphical user interface. For example, touch screens typically include a software-defined keypad (“soft keypad”) displayed on the touch screen and a touch sensing mechanism for detecting when the touch screen is touched by a finger or stylus to input a key function. Exemplary touch sensing mechanisms include analog resistive, infrared, acoustic, capacitive or electromagnetic inductive sensors. Effective operation of a touch screen requires visual feedback to the user to locate and select menu items and other software-defined keys on the touch screen. However, for some users and in some situations, visual feedback may not be sufficient to determine that a key has been selected.
One solution for providing improved touch screen feedback is described in U.S. Pat. No. 5,977,867 to Blouin. In the Blouin patent, a vibrator is attached to the touch screen to provide a tactile vibrating sensation to the user when a key on the touch screen is selected. The vibrator vibrates for a time that is long enough for the user to feel the sensation, but short enough to terminate before the next key touch.
However, the Blouin touch screen design still requires visual feedback to the user to locate the key on the touch screen prior to touching the key. In some situations, it is desirable for the user to be able to locate keys without looking at the touch screen. For example, when driving, a user may prefer to locate and select a menu item or locate and dial numbers on a software keypad using only tactile feedback in order to maintain visual contact with the road. As another example, a vision-impaired user may be unable to operate a touch screen having key locations without tactile feedback. There is therefore a need for a tactile feedback mechanism to assist a user in locating keys on a touch screen.